A tape measure is a flexible form of ruler. The tape measure consists of a ribbon of cloth, plastic, or metal with linear-measure markings, often in both imperial and metric units. Tape measures designed for carpentry or construction often use a stiff, curved metallic ribbon that can remain stiff and straight when extended, but retracts into a coil for convenient storage. A tape measure of 3 to 100 feet can wind into a relatively small housing. This type of tape measure will have a floating end hook to aid in measuring. The end hook consists of a tang and a hook. The tang is designed to float a distance equal to the hook's thickness, to provide both inside and outside measurements that are accurate.
In many instances, measurement accuracy is essential to creating a quality finished product. For example, in cabinetmaking, a series of 1/16″ errors in cutting 8 pieces could result an assembled cabinet which is ½″ too large or ½″ too small. The combined discrepancies add up to significant errors. A set of cabinets that are ½″ too big won't fit the opening they were designed for, thus causing loss of time and money to modify or remake the cabinets.
The accuracy of tape measures is particularly important when several tape measures are being used by different people or at different locations. For example, a cabinetmaker makes a cabinet door, then orders glass to fit it using a tape measure. The glass company cuts glass for the same cabinet door using their tape measure. If one or the other has not used an accurate tape measure, the glass will not fit in the door as designed.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.